Alpha-methylene-gamma-butyrolactone and methyl alpha-methylene-gamma-butyrolactone are useful monomers in the preparation of both homopolymers and copolymers. In addition, the alpha-methylene-gamma-butyrolactone group is an important structural feature of many sesquiterpenes of biological importance.
U.S. Pat. No. 6,232,474 B1 describes a method for converting certain starting lactones to alpha-methylenelactones using a homogeneous or heterogeneous so-called basic catalyst that can be selected from the metal oxides, hydroxides, carbonates and phosphates, any of which may be supported or unsupported. The preferred reaction is the conversion of gamma-butyrolactone to alpha-methylene-gamma-butyrolactone. The basic catalyst may include additives and promoters to enhance catalyst efficiency. The method involves a reaction between the starting lactone and formaldehyde and may be carried out in a batch mode, optionally using an organic solvent and a phase transfer agent. The method is carried out at a temperature of at least 70° C. and a pressure less than or equal to 2000 psi (13.7 MPa).
The prior art in this area involves the use of supported catalysts on silica, which are known to be hydrothermally unstable (see for instance, WO9952628A1). Under reaction conditions, or after repeated regeneration cycles, a hydrothermally unstable material will show catalytic performance that will deteriorate with time.
Aluminum phosphorous oxynitrides are a relatively new category of materials, which may have unique properties for base catalyzed chemistry. These materials are believed to have adjustable acid/base properties. These phosphorus oxynitrides, which were first described by M. J. Climent (M. J. Climent et al., Catalysis Letter, 59 (1999)33–38; P. Grange et al., Applied Catalysis A: General 114 (1994) L191–L196; P. L. Grange et al., Applied Catalysis A: General, 137 (1996) 9–23) have been shown to be active for various base catalyzed condensation reactions (e.g., arylsulfones with substituted benzaldehydes). Structural information is not available. However, depending on the nitridation temperature and other conditions, and therefore degree of incorporation of nitrogen into the structure of these materials, it was shown that the relative proportion of acidic and basic sites in the catalyst could be adjusted. However, the use of these materials for lactone conversion has not been described, either as the oxynitrides or as composite catalysts in which various Group I and/or Group II elements are incorporated into the oxynitride.
Although a phosphorus oxynitride system might be expected to possess a significant advantage in hydrothermal stability compared to conventional silica catalysts, the catalytic activity of such a material for lactone conversion reactions cannot be predicted because of the unpredictable nature of catalysis in general.
It would be advantageous to have a catalyst that is hydrothermally stable at high temperatures and whose activity does not decay with time on stream (TOS) or after several high temperature oxidizing regenerations.